Memory devices, such as flash memory, are widely used in computers and many electronic products. Such memory devices have numerous memory cells. Information can be stored in the memory cells in a write operation. The stored information can be obtained in a read operation or can be cleared in an erase operation. In some conventional memory devices, the read, write, and erase operations may generate excess carriers (e.g., holes) and cause them to accumulate in some active areas of the memory device. Such excess carriers may affect the reliability of these operations.